36 CHICAGO ACADEMY OF SCIENCES. 



followiii'g' section of a well in Sec. 8, Crete Township, is represent- 

 ative: 



1. Yellow, pebbly clay ' 15 feet 



2. Blue, pebbly clay. . . ■ • 8 



3. Dry sand ..-..• 12 



4. Quicksand and water. • 17 



Depth ■ • • • • 52 feet 



In some wells tlie sand lies witliin ten feet of the surface and 

 has no blue clay above it. 



The following sections of well boring's near Spencer will il- 

 lustrate the structure and show the general fhickness of drift in 

 that locality: 



Section of well at elevator in Spencer — 



1. Yellow, pebbly clay • • • • • 12 to 15 feet 



2. Blue, pebbly clay, hard and dry 50 " 



3. Cemented sand 3 to 4 " 



4. Quicksand . . • • 5 to 6 " 



5. Limestone at 75 feet (i) ••..-, 



Section of well two miles south of Spencer — 



1. Yellow, pebbly clay. 8 feet 



2. Sand and gravel. 14 " 



3. Blue, pebbly clay, hard and dry 60 " 



4. Limestone at 82 feet . 



Carbonic acid gas has been encountered quite frequently 

 in wells along this moraine. It is usually found in dry cavities 

 in the blue clay and is struck at various depths. 



In the outlying belt in Will County, from the Des Plaines 

 River southeastward, the thickness of the drift is much less than 

 in the main belt, being as a rule between forty and seventy-five 

 feet. There is usually at surface ten to twenty feet of yellow till. 

 Beneath this is occasionally found a bed of sand or gravel of 

 slight depth, but usually blue till immediately underlies the yel- 

 low. In the blue till beds of blue quicksand are often struck. 

 These beds are, in this district, sometimes ten feet or more in 

 depth, and ofifer great obstruction to well-dig-ging or boring. 

 Such quicksand is not uncommon in .other districts in Northeast- 

 ern Illinois. Wells are seldom obtained in it, though it is full of 

 [n It is thought that rock was struck.at the bottom of the well. 



